Improved process of purifying iron and steel



UNITED STATES PATENT OEEICE.

JOHN F. BENNETT. OF PITTSBURG, PENNSYLVANIA.

IN'IPROVEDl PROCESS OF PURIFVING lRN vAND STEEL Specification forming part of Lettere Patent'No'. 75,240, dated March, 10,` 1868'; antedaterl February 28, 1868.

To all whom it may concern: y

' Be it known that l, Jouir F. BENNETT, of the city of Pittsburg, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in the Process of Desulphuriz'iug and Purifying IronA and other metals; and'I do hereby declare the following to bea full, clear, and exact description thereof.-

My invention consists in `an improvement in the manufacture of iron and steel by what A is known as the pneumatic' process, the object'V being tc'carry oft' the sulphur, phosphorus, and other impurities from the metal, which arenot removed by that process as ordinarily conducted. This result I effect while the met# al remainsin the converter, and without sub` jecting it to a process of reheating. Pig metal .-.on crndeirommhiclrresltsirom-.theprocess.

'l of deoxidizing the ironore by means-of ablast. furnace', is' highly-earhonized ironwith 'which are mingled silicon, sulphur, phosphorus, and other impurities.

The atmospheric pneumatic system consists in the removal of the excess of carbon from the metal by subjecting it, while in a molten condition, to the direct action of an atmospheric blast for the purpose of burning out `the-carbon, without `theuse of separate fuel for 'supporting combustion and producing the f requisite heat.

The melted crude iron is poured into-a receiver zii-.converter at a temperature of about 30000 Fahrenheit, and a blast'of atmospheric air, ata pressure of 'about twenty pounds to the square inch, is forced through the melted metal, entering at kor near the bottom of the converter, and permeatingthe mass of molten metal therein. .The ymechanical effect of the' passage of air through' the metal is to produce 'violent ebullition and commotion, and the chemical ecct is that the oxygen of the air unites with the carbon of the iron, generating a. great increase of heat and causing a vivid combustion, the carbon of. the iron serving, together with a portion of the iron as the fuel, and the carbon being thus burned out and removed.4 During this process, whichy ordina rly takes about sixteen minutes, the heat of the metal rises rapidly to about 50000 Fehry enheit,"and as soon as the carbon' is all consumed the blast of air is stopped, as otherwise a rapid oxidation of the metal would ensue.

This process, which is successfully employed Vin the manufacture ot steel from crude ironi does 'not eect the removal off the sulphur an phosphorus, which are eliminated, if at'all, by

-a subsequent and distinct operation. I propose to elect the removal of the sulphur and 'The'.accompanying drawing represents they apparatus whichl." propose to employ, which is similar, in many of its details, to that used.` inthe pneumatic process.

1, In the drawing, A'is the converter, an egg?y shaped 'iron vessel, exactly likeV that used in the atmospheric pneumatic process. It is supp orted on pillar-.blocks a by trunnions 'placed *above the centerof gravityof the vessel, so

as toinclineit to preserve a vertical position and yet permit it to be tilted over in order to pour out the metal at the close of the opera-j tion. One trunnion, c, is hollow, andc'ommulnieates externally with the blast-pipe el and internally with the interior of thefconverter 'bymeans of a passage, b, which conducts the blast totuyere-holesin the bottom of the ognverter A. B is the`blast-cylinder, of ordinary construction, by which'a blast of air,3 or,of

vycarbonio-acid gas, or both,I as 4the 'case may he, is forced through the blast-pipe d into the converter A. Theinlet-pi e e admits atmospheric 'air into the blastc linder B through the vvalve-chest j', and the inlet-pipe g, oonneeted with the gas-holder D, admits the'earbonie-acid gas. IThe cock or yalve i serves to regulate the supply ,of air or gas to the blastcylinder, .and also to shut on' either or both, fc that. by turning it properly, either gas or air alone, or a mixture of the two, may be admitted into the blast-cylinder and forced into the converter.

The carbonio-acid gas employed in my process may be manufactured by the action of muriatic acid upon limestone, in a suitable -'apparatus, when it is desired to use the gas pure; but Where it is employed in combination with the nitrogen of the air it may be conveniently procured b'by means of a generatingoven, E, which consists of a close-arched chamber furnished with grating, forminga bedi'or coke or charcoal, which being ignited, a stream Vof atmospheric air is forced, by a fan, h, into the closedspace under the grating or iire-bed, and the air, passing through the f ignited carbon, combines with it and `is converted'into carbonic acid mingled with nitrogen, which thence passes through the pipe 7o into the gasholder D, which is of ordinaryconstrnction. The inlet-pipe g of the blast-cylinder B opens into the gas-holder D.

The operationof my improvement is as follows: The atmospheric pneumatic process as ordinarily practiced is carried on substantially as before described, the valv'es t being set so as to-forceatmospheric air through the melted metal in the converter. This is continued until the carbon is nearly -all 4 removed, which lwill be usually i about sixteen minutes,l the i 'time varying in practice witheach charge of metal according to its heat when poured into the converter, thequantity of carbon whichr it contains, the pressure ofthe blast, and other variable causes. A's soon as the process of 'decarbonizationis about completed I stop the blast of atmosphericair, and, by means of the' valve force a blast of carbonicacid gasfrom the gas-holder D through-the melted metal in the converter A. This blast is continued for half a minute, more or less. Ithen again chan ge the blas admitting atmospheric airpwhich is continue for about fifteen seconds, when the blast is stopped, the operation being complete. In order to preserve' the distinctness and purity of each kind of blast,'botlithe air and carbonio-acid gas being introduced through the same pipe d and trunnion c intotheconverter, I tilt the converter over on its tr'unnl ions, just before changing the blast, until the tuyere-holes are no longer covered by the melted metal, and allow the changed blast to pass through the converter.:without entering the metal until all traces of the former blast have disappeared, when the converter is restored to its upright positionv and the process The ,resultwhi'ch -I accomplish by my improvement may beybriey stated thus: lThe blast of atmosphericV air being lcontinued through the molten iron until nearly all' trace of carbon has disappeared, on thel introduction of the .carbonicfacidgas a chemical union is formed between the two equivalentsof oxygen .and the sulphurpresent in the iron, forming sulphurous acid, which passes ol' as gas, de-

positing the carbon thereby set free, which may be expressed thus: G D21-+S S 02+ A similar result takes place inrespect to phos-A phorus present as, an impurity in the iron. The oxygen of the carbonio acid combines with the phosphorus, evolving acid gases of phosphorus and depositing carbon, thus: 2 G O2 l? P O4 2 (l, and carbon is deposited. #This deposit of free carbon may be left in the iron, if preferred, in the manufacture of steel; or it may be burned out, after the sulphur and phosphorus are removed, by a repetition of the atmospheric blast for a few secondsas before stated. The oxygen of the carbonio-acid gas Will also combine with the iron, forming fer-r 'rous acid, thus: (l 02+ Fe=2 Fe O G, theformation of the protoxide of iron setting free and depositing the carbon.

- In practice it-will befonnd that the sulphur f l and phosphorus will first be expelled, and that what little carbon is deposited will eitherbe blown voli' by the blast or current of air-,or gas,

lor will unite'with the ferrous acid, reducing it to iron and forming -carbonic oxide, which will. be evolved as gas. `While the blast of carbonio-acid gas is passing through the molten i iron the temperature of the metal will fall somewhat, losing almost onefourth of the ad-l ditional heat gained during the passage of the i latmospheric blast. This, however, isgrather f an advantage than otherwise, as it is found l that by the atmospheric pneumatic process the iron is .rendered almost too fluid by the4 extreme heat. If preferred, the carbonio-acid gas may be heated before entering the converter.4 'i f A modification of the process which I have `described consists in allowing a small proportion of carbonie-acid gas to enterthe blastcylinder, together with the air, and thus subjecting the molten crude iron to a combined blast of atmospheric air and carbonio-acid gas.`

inbefore described paratus shown in th cylinder. V

Carbonio-acid gas mayralso be used to ativan; tage in removing sulphur andzother impurities@ from the sulphnrets of copper, yzinc', nickel,'f and other metals by passing it, asa blastor current, through the metals ywhen in' aniol'teirl state.

- f Beursnieksic1-1ia1 intestati) 'what I claim as my inventionLimd desire to sewill form chemical combinations with the oxyeure by Letters Patent, isgen ofthe carbonio acid and deposit the carbon,

The use of cerbonicaicid ges, either alone or substantially as hereinbefore described. mixed with atmospheric einer with other gases In testimony whereof l, the seid JOHN F. or vapors, when introduced into the body of BENNETT, have hereunto set my hand.

molten iron or other metal, in combination JOHN F. BENNETT. with or'immcdietely following the pneumatic `Witnesses`: process, for the purpose .of removing sulphur, A. S. NICHOLSON,

phosphorus, and any other impurities which G. H. GHMSTY. 

